1. Field of the Invention
The present invention relates to a liquid-crystal display device and a method of manufacturing the liquid-crystal display device.
2. Description of the Related Art
Liquid-crystal display devices have advantages, such as low profile, light weight, and low power consumption. Thus, liquid-crystal display devices have been often used in mobile electronic devices, such as mobile phones or digital cameras. Liquid-crystal display devices include a liquid-crystal panel having a liquid-crystal layer sealed between a pair of substrates, so that light emitted from a planar light source, such as a backlight, provided on the back side of the liquid-crystal panel, is modulated by the liquid-crystal panel. Then, the modulated light enables an image to be displayed on the front side of the liquid-crystal panel.
In recent years, liquid-crystal display devices including a touch panel via which content designated by a user can be input by the user by directly touching an icon displayed on the screen of a liquid-crystal display device have been used.
This touch panel is disposed on the uppermost side of the liquid-crystal display device so that the designated content shown on the screen of the liquid-crystal display device can be selected by directly touching it with the hand of a person or with an object. In the touch panel, the position at which the hand or the object contacts therewith is detected, and by using the content designated at the contact position as an input signal, the liquid-crystal display device is driven. It is not necessary for a liquid-crystal display device including a touch panel to separately have an input device, such as a keypad, in a case where it is used in a computer or the like, is used in an input device, such as a keyboard or a mouse, or is used in a mobile product, such as a mobile phone. As a consequence, touch panels are increasingly being used.
On the other hand, in products including a touch panel as a result of being arranged on the liquid-crystal display device, a decrease in optical characteristics occur due to an increase in device thickness or size and due to influences of the refraction surface. Furthermore, there is a problem of an increase in the manufacturing cost due to the fact that a touch panel is necessary in addition to the liquid-crystal display device, and it has been suggested that the liquid-crystal display device and the touch panel be integrally formed.
In recent years, such liquid-crystal display devices having a so-called sensor function, in which a liquid-crystal display device and a touch panel are integrally formed, have been proposed. In one liquid-crystal display device having a sensor function, in Japanese Unexamined Patent Application Publication No. 2007-95044 described below, a method has been described in which an external pressure that is generated when a hand or an object contacts the liquid-crystal panel of a liquid-crystal display device is detected by electrical contact between a pair of substrates forming the liquid-crystal panel.
FIG. 10 shows a schematic configuration of a liquid-crystal display device 100 having a sensor function of the related art. The liquid-crystal display device 100 having a sensor function of the related art is configured to include an array substrate 101, an opposing substrate 102 provided so as to oppose the array substrate 101, and a liquid-crystal layer 103 provided between the array substrate 101 and the opposing substrate 102.
The array substrate 101 will be described first.
The array substrate 101 is configured to have an insulation substrate 104 formed from glass in the shape of a transparent rectangular flat plate, and thin-film transistors (hereinafter TFTs) 107 formed of a plurality of switching elements that are formed so as to correspond to pixels on the insulation substrate 104. Then, on the TFT 107, a pixel electrode 106 that is connected to the TFT 107 through a contact part 118 formed on a planarization film 105 for covering the TFT 107 so as to achieve planarization is pattern-formed on the planarization film 105. Furthermore, an orientation film 108 is provided on the pixel electrode 106.
Next, a description will be given of the opposing substrate 102.
The opposing substrate 102 includes a transparent insulation substrate 109, such as glass or polycarbonate (PC), a color filter layer 110 formed on one main surface of the insulation substrate 109, and a planarization film 111 formed on the color filter layer 110. Furthermore, a sensor adjustment layer 115 in a projecting form, and a common electrode 112 formed on the entire surface including the sensor adjustment layer 115 are provided on the planarization film 111. Furthermore, a spacer layer 114 formed to maintain the thickness of the liquid-crystal layer 103, and an orientation film 113 formed on the entire surface excluding the spacer layer 114 are provided at a predetermined position on the common electrode 112.
The color filter layer 110 is formed of a resin film in which dyes or pigments having the three primary colors of red (R), green (G), and blue (B) are contained.
The planarization film 111 is used to planarize the surface of the color filter layer 110 and is formed from a light-transmitting material.
The sensor adjustment layer 115 is formed in a projecting form at a predetermined position on the planarization film 111, and is formed to have a value smaller than the cell thickness (the thickness of the liquid-crystal layer 103). The common electrode 112 is formed on the entire surface containing this sensor adjustment layer 115. In an example of the related art, a sensor electrode 116 is formed by the common electrode 112 formed on this sensor adjustment layer 115.
Furthermore, the spacer layers 114 are formed in a spaced manner at equal intervals on the common electrode 112, and are formed in a columnar shape at a predetermined height of a cell thickness. These spacer layers 114 enable the cell thickness between the array substrate 101 and the opposing substrate 102 to be maintained.
The opposing substrate 102 and the array substrate 101 are formed so as to maintain a predetermined cell thickness and so as to oppose each other in such a manner that the respective orientation films 108 and 113 face inwardly. This cell thickness is maintained constant on the surface by the height of the spacer layer 114, and as a result of a predetermined liquid-crystal material being sealed within this cell thickness, the liquid-crystal layer 103 is formed.
In the liquid-crystal display device 100 having the above configuration, the sensor electrode 116 and the pixel electrode 106 at a position opposing the sensor electrode 116 constitute a touch sensor.
In the liquid-crystal display device 100 shown in FIG. 10, pressure is applied by pressing the opposing substrate 102 using a touch object 117, such as a hand or a finger. Then, the sensor electrode 116 is brought into contact with the pixel electrode 106 of the array substrate 101 opposing the sensor electrode 116 via the orientation films 108 and 113. By detecting contact between the sensor electrode 116 and the pixel electrode 106, it is possible to detect the position touched by the touch object.
In such a liquid-crystal display device 100 having a sensor function of the related art, the electrical connection of the sensor electrode 116 and the pixel electrode 106 enables the position touched by the touch object 117 to be detected. Thus, the smaller the distance between the two electrodes, the easier the detection of the touched position with the application of a small external pressure. For this reason, for the liquid-crystal display device 100 having a sensor function of the related art, as shown in FIG. 10, many examples can be seen in which a sensor adjustment layer 115 formed in a projecting form is formed on the planarization film 111, and the height of the sensor electrode 116 is adjusted.
However, regarding the area of bonding between such a sensor adjustment layer 115 in a projecting form and the planarization film 111 that is a layer below the sensor adjustment layer 115, securing of the bonding strength is difficult because the bonding area is often a very small area on the order of several microns in diameter.
Furthermore, the spacer layer 114 in a columnar shape is often formed on the common electrode 113. In general, the degree of contact between the common electrode 113 and the spacer layer 114 is weak, and the spacer layer 114 is easily peeled off.